1. Field of the Invention
The present invention generally relates to systems and methods for detecting defects on a wafer, which are particularly useful for detecting repeating defects in array regions on the wafer.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
Inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to promote higher yield in the manufacturing process and thus higher profits. Inspection has always been an important part of fabricating semiconductor devices such as ICs. However, as the dimensions of semiconductor devices decrease, inspection becomes even more important to the successful manufacture of acceptable semiconductor devices because smaller defects can cause the devices to fail.
Some current inspection methods use standard images such as standard die images to detect repeater defects on wafers. Repeater defects are normally caused by foreign objects on a reticle/mask. After a wafer is printed with this kind of reticle, the defect appears on all dies. A die-to-die comparison inspection will fail because the defects on all dies will cancel each other resulting in weak or no signal from the defect. A standard die image (also commonly referred to as a “golden die”) may be compared to a test die image acquired for a wafer being inspected and the results of the comparison may be input to a defect detection algorithm or method to determine if any defects are present in the test die. Such golden die images are commonly used for inspection of logic regions of dies since the logic regions of dies often do not include periodically repeating features that can be compared to one another for defect detection.
A disadvantage of using a standard die image for inspection is that, if the standard die image was acquired from a wafer other than the one being inspected, wafer-to-wafer noise can be relatively high and can interfere with defect detection or decrease the sensitivity of defect detection. In addition, if the standard die image is acquired using the same wafer that is being inspected, die-to-die noise can also interfere with, or decrease sensitivity of, defect detection. Furthermore, if the standard die image is generated using design data for the wafer, the standard die image may not adequately represent noise sources on the wafer thereby having the same disadvantages described above.
Accordingly, it would be advantageous to develop systems and methods for detecting defects on a wafer that do not have one or more of the disadvantages described above.